A punch tool including a plurality of punches circularly arranged has a configuration in which a plurality of punches are circularly arranged in a casing attachable to and detachable from a rotating holder mounted on a punch holder rotatably in a punch press, and a striker capable of freely striking each punch is provided to be vertically movable in the upper portion of the casing. An example of a corresponding prior technique is disclosed in Japanese Patent Application Laid-open No. H8-155561.
In a configuration described in the above patent publication, a plurality of punches are supported to be vertically movable in a punch mounting portion in the casing, and a head portion of each punch is engaged with a peripheral groove having a cross-sectional shape of a T-shape formed on a striking plate corresponding to the striker. When punching work is performed on a workpiece by each punch, a stripping force for drawing the punch from the workpiece acts on a central portion of the striking plate.
Therefore, when the punch is drawn out of the workpiece, an unbalanced load acts on the punch and a bending moment acts thereon, which can cause a jamming phenomenon on a slide guiding portion, such as a sliding portion of the punch or the striking plate. In the configuration of the Patent Document 1, an elastic member is arranged opposite to the center of the lower face of the striking plate. Therefore, a problem arises that it is difficult to doubly arrange a plurality of punches along an inside circle and an outside circle, so that it is difficult to arrange more punches.
The present invention has been achieved to solve the above problems, and an object of the present invention is to provide a punch tool where an unbalanced load does not act when a punch is drawn out of a workpiece after punching work, and more punches can be arranged.